PC Graphics

[Sentry]

I have a Ryzen 5700G and I am using an ASUS B550 motherboard with 3 video outs (2 DisplayPort and 1 HDMI). I have no dedicated video card.

I can drive three displays at the same time. And each output can successfully drive a 4K display at 60hz if it's the only display. But I cannot run 3 displays at 4K at 60hz, and the limitations I am running into are not clear to me.

I can run two 4K displays at 60hz. If I add a third display of any type, the maximum refresh rate choice for the two 4K displays drops to 30hz. Also, the resolution on the third display might be limited to something less than its maximum resolution.

Also, if I run just one 4K display at 60hz, and have two other 2K monitors connected, the max refresh rate on those 2K monitors drops from 75hz to 60hz. Or, I have to run the 4K monitor at only 50hz.

So, it's not completely shocking that nobody cares about running 3 x 4K with integrated graphics. But there is nothing in the spec of the processor or the motherboard that I see that would prevent this from happening. What is going on here? Specifically, what limits the refresh rate? And, is this correct behavior?

[agates]

I have the same problem, trying to drive a 1080p@144Hz DisplayPort monitor with a single 2160p@60Hz display over HDMI, which is getting limited to 30Hz.  So the issue isn't limited to running triple 4k displays.

I'm running an ASrock B550M Pro4 with bios version 2.20

[Sentry]

I have a theory but I haven't been able to prove it myself. I did the math on the required display bandwidth and my system memory bandwidth and they came out really close. I noticed that my motherboard defaulted to running my PC3200 RAM at only 1000mhz instead of 1600, with tighter timings than the XMP profile said it would get. There's a chance that this caused the memory bandwidth to be too small to push the resolution and refresh rate needed. I'm betting that if I run it at spec, it will increase the bandwidth and allow higher refresh rates in all combinations. 

[elstaci]

The Maximum Displays that the Ryzen 7 5700G supports is 3 Displays at one time.

Also I believe the Motherboard sets the specs as far as Resolutions goes depending on the APU you have installed.

@agates- Here is his ASRock Motherboard specs Maximum Resolutions on his Motherboard: https://www.asrock.com/mb/AMD/B550M%20Pro4/index.asp#Specification

So, in my opinion, if Agates has two 4kx2k monitors connected it will work at 30Hz rather then at 60hz to get the same Resolutions.

Using DP Port he should get higher Resolutions on 2-3 Displays, depending which Resolution he chooses.

@SentryI don't know the exact Asus Motherboard you have so I couldn't see what the Maximum Resolutions are for you Motherboard.

IF you run at lower Resolutions like 1920x1080 you might be able to get 60Hz on 2-3 Displays on the DP: Port. Since 3 - 1920 equals 5760 which is within Agates Maximum Resolution for DP. as an example.

[Sentry]

What is your source on Ryzen supporting 3 displays? I think it has 4 display drivers, actually. But I also don't have a source on that.

[elstaci]

Don't know how reliable this Tech site is but:

This is where I found that information from: https://www.cpu-monkey.com/en/cpu-amd_ryzen_7_5700g-1876

Sometimes Wikichips or CPU World shows the Maximum Supported Display but not on this processor. You need to check Vega 8 Graphics.

I looked up the 4700G and at WikiChips it says it supports 4 Displays maximum: https://en.wikichip.org/wiki/amd/ryzen_7/4700g#Graphics

So it is possible that CPU-Monkey might be in error. For the 4700G CPU-MONKEY also shows 3 displays Maximum supported.

While WikiChips shows 4 Displays Maximum.

[elstaci]

I would open a AMD Service Request (AMD SUPPORT) and see if they mention how many maximum Displays the 5700G supports from here: https://www.amd.com/en/support/contact-email-form

[agates]

@elstaci I'm only trying to run two displays, albeit at two different resolutions and refresh rates.

Regardless, I will open a service request.

EDIT:  If it makes a difference, I'm running from linux with the open source driver stack.

[elstaci]

@agates 

Yes that does make a huge difference. 

Someone with Linux experience will need to help you.

[agates]

I mean if it's a firmware limitation it wont matter whatsoever... just trying to see if it's a common variable, however.

[elstaci]

If you are just trying to connect 2 displays then that shouldn't be an issue. The issue that might arise is that both have different Resolutions & Refresh rates.

Generally it is best to try and run all the displays with the same Resolutions and Refresh rates for best compatibility.

How you can configure Linux to run Multi-Display I really have no idea. Like I mentioned someone else will need to help you.

Phoronix is a popular Linux Website for AMD Drivers that you might want to check out and ask your question at their forum: https://www.phoronix.com/forums/